Silver and copper are widely used in a variety of product applications. Unfortunately, where these metals are exposed to the atmosphere they typically corrode or tarnish quite rapidly due to the presence of oxidizing materials and sulfides. They also corrode when exposed to components of perspiration (e.g., chloride ions and acids).
The tarnishing or corroding of these metallic surfaces is not only unsightly, it also interferes with desirable physical properties of the article. For example, plastic film bearing a silver surface coating is very useful as static shielding in packaging applications. However, when the silver coating corrodes it loses its conductivity and becomes worthless for its intended use. Also, when the silver layer in a mirror becomes corroded or tarnished the mirror loses its effectiveness and primary utility. Similarly, in many other product applications, the tarnishing or corroding of a silver or copper surface or layer is regarded as very detrimental.
Over the years a number of compounds or compositions have been proposed for treating silver and copper surfaces. See, for example, U.S. Pat. Nos.: 2,475,186; 3,330,672; 3,361,581; 3,365,312; 3,506,699; 3,640,736; 3,663,561; 3,687,713; 4,058,362; 4,234,304; 4,255,214; 4,357,396; and 4,645,714. However, none of these patents have described the use of the compounds or compositions described herein.